A 16-year-old girl comes to the office due to a skin condition. For the last 3 years, she has had small "pimples" on the posterior surface of her upper arms. The lesions are associated with mild pruritus during the winter months but are otherwise asymptomatic, and the patient is primarily concerned due to their appearance when she wears short-sleeved tops. Medical history is unremarkable, and the patient takes no medications. Examination findings are as shown in the exhibit. Which of the following is the most likely diagnosis of this patient's skin condition?

Question

A 16-year-old girl comes to the office due to a skin condition.  For the last 3 years, she has had small "pimples" on the posterior surface of her upper arms.  The lesions are associated with mild pruritus during the winter months but are otherwise asymptomatic, and the patient is primarily concerned due to their appearance when she wears short-sleeved tops.  Medical history is unremarkable, and the patient takes no medications.  Examination findings are as shown in the exhibit.  Which of the following is the most likely diagnosis of this patient's skin condition?

Quizplus · Accepted Answer

This patient has a chronic skin condition consistent with keratosis pilaris (KP), a benign condition characterized by retained keratin plugs in the hair follicles. It presents with small, painless papules, a roughened skin texture, and mottled perifollicular erythema. KP can occur anywhere on the body but is most common on the posterior surface of the upper arm. It is usually asymptomatic, although small pustules or pruritus may sometimes occur; exacerbations are common in cold, dry weather. KP can occur alone or in association with atopic dermatitis or ichthyosis vulgaris (an inherited disorder characterized by chronically rough, scaly skin). The diagnosis is typically obvious based on appearance and clinical history. Treatment, when necessary, includes emollients and topical keratolytics (eg, salicylic acid, urea). (Choice A) Folliculitis (bacterial or fungal) is due to inflamed hair follicles and typically causes an acute, erythematous, pustular eruption. The lesions can be asymptomatic or cause significant pruritus and pain. This patient's chronic course and absence of significant inflammation make folliculitis less likely. (Choice C) Miliaria (heat rash) is due to blockage of the eccrine sweat ducts in the setting of increased heat or humidity. It is most common in newborns and young children; manifestations can range from small, thin-walled vesicles to patches of erythematous papules or pustules. erythematous papules or pustules (Choice D) Pseudofolliculitis presents with small, painful papules caused by growth of the hair shaft into the perifollicular skin. It is most common in individuals with tightly curled hair and occurs in the beard or other areas where the hair is shaved closely. (Choice E) Papulopustular rosacea presents with small papules, pustules, and skin sensitivity. It typically affects the convex surfaces of the central face, and symptoms are often aggravated by hot or spicy foods, alcohol, sun exposure, or high ambient temperatures. Papulopustular rosacea Educational objective: Keratosis pilaris is characterized by retained keratin plugs in the hair follicles. It occurs most commonly on the posterior surface of the upper arm and manifests as small, painless papules; a roughened skin texture; and mottled, perifollicular erythema. Exacerbations are common in cold, dry weather. Treatment includes emollients and topical keratolytics (eg, salicylic acid, urea).

A 16-Year-Old Girl Comes to the Office Due to a Skin